I’ve been playing around with my Simple-Fire design and last night got a 1.5 hour run that normally last 30 minutes. I mounted the 15 gallon grease drum that is the gas generator, on top of the frame that holds the Kolher 7Kw gen set. The gas filter is located next to the gas generator. The idea is to get the gas generator off the floor, make the genset more compact and use the engine vibration to prevent any bridging of charcoal. I also replaced the sump pump hose going from the gas out let and used flexible steel exhaust tubing. This allows me to run the gas generator when the gas exit temp is above 150F. The final result was I still burn one pound of charcoal every 10 minutes, but with the vibration and high temp gas outlet hose, I could burn up more charcoal without melting the sump pump hose. This is such a nice setup that I am going to convert my Gravely to a steel gas hose too.
Here is a picture the following day of how much charcoal was used on that run. Also a view of the Kent style nozze I am using in this Simple-Fire. It is holding up very well so far. I still use exhaust gas to cool down the oxidation zone. Got to really ramp up my charcoal making this year! Just love lighting up my shop with charcoal!
Gary in PA

Gary, I’m very interested in getting information on gasifying stationary engines. I’m going to start a build on a gasifier to power a 30 KW Onan Gen-set (1967) with nan auto-transfer switch. It is powered by a 240 CI Ford Industrial engine rated at 120 HP. I am very new to this so am truly below a novice level. Just went out and purchased a Lincoln 140 Mig/Tig welder and stuck my first pieces of metal together. Please don’t ask for pictures (very ugly welds . However I am committed to getting this done and any input would be so appreciated

Hi Michel, The first decision you have to make is do you want to run your genset with a wood gasifier or a charcoal gasifier. They both have advantages and disadvantages which a little research will show. Since you are on the charcoal gasifier portion of this site, I will comment on running your gen set on charcoal. You have a fairly large set that can be run with a Simple-Fire style generator, but scaled up. Having never made a unit to run such a large engine, I will only be making an educated guess at nozzle size. Here goes.
You will be using a 55 gallon drum as the gas generator. The nozzle will be 1 1/2 or 2" iron pipe. The gas outlet will be 2" and go into a filter that is at least the size of a 5 gallon pail. This gas outlet is centered on the removable lid of the 55 gallon drum. Or, you can pull the gas out the side of the drum, as close to the top as possible using the same pipe nipple/flange setup that the nozzle is attached to. Use at least at least 8 feet of flexible steel exhaust hose to carry the charcoal gas from the generator to the filter. This extra length will help cool the gas as it gets hotter. Provide for exhaust to return to the air inlet of your gas generator to cool down the reaction.
If your genset was setting in my yard, we had the drums and other materials, we could have it running on charcoal within 8 hours. What I am saying here is a charcoal gasifier is very simple to build. You will need lots of charcoal to run an engine of this size. My 7kw goes through 1 pound of aspen charcoal every 10 minutes. This is enough charcoal to fill a one gallon container. A unit your size may consume that same amount of charcoal in two minutes.
Another thought is to go ahead and make a charcoal gasifier and get your genset running without a big investment in time and materials. You get your feet wet on running a gasifier and start to realize all the fun it is. Then, consider building a wood gasifier.
Until later,
Gary in PA

Although Gary’s simple fier is a grand idea…I think the majority of the time would be used for making charcoal…as a unit this big will use about 200 lbs of charcoal in 6-8 hours…and you need a lot of wood to make that much charcoal…plus look at all the wasted energy you loose just making charcoal …I have a 7.5 k generator with a 14.5 hp…I have a modified Fema to WK style woodgas generator…I use about 10-15lbs a wood an hour …

Hi Michel, As a middle of the road option you could choose to build Gary’s bigger unit which while it runs on charcoal can be supplemented by other fuels to reduce your charcoal usage. Of course at the size engine you are talking and a stationary application you are probably more suited to the raw wood gasifiers eventually. I run a 55 gallon simple fire type unit with softwood charcoal and a second 55 gallon drum as a cooler/dust remover/filter unit and it works great for me using a 13 hp generator at half load. For you you would want to increase the cooling area and dust collection; perhaps a 3rd 55 gallon barrel. Be careful of the grin you get when it first fires up though; its very wide… attached are a few pics of the new filter unit 1st foam inserts, 2nd unit showing slotted base for holding in charcoal, 3 barrell housing showing diversion of gas to make it circle and cool…

I have had some real world expereince with HOT charcoal gasifing an IC engine. Wanted to see how hot of input fuel gas it could handle. HOT gas capability would greatly reduce cooling and condesate handling needs. Late 70’s and later modern vehicle engines even have hot and cold air blending systems to try and give the engine an even steady HOT intake air to make emmisions controls more consistent and reliable. They target for ~175F blended temperatures. They have to be concerned with liquid fuel droplet vaporization in the inlet passages. Backfire booms.
150F sucked fuel gas is very safe. Up to 225F OK with modern engine oils. Past 250F the intentional oil film on the intake valve stem will vaporize and carbonize resulting in excessive intake stem and guide wear. One the reasons why the exhaust valves generally wear quicker! This temp oil burning off in what is intended to be a cooling off cycle aslo seems to promote quicker cycliner and piston skirt wear.
Another problem ran into is the added heat into the engine core also seems to cause the springy ductile piston rings to heat anneal soften “collaps” with loss of compression. This will first show up as hard starting, then loss of engine power, lots of crankcase pressure build up blow-by.
Just a heads up. There are limits to allowable intaked gasses heats depending greatly on the actual engine and essecially how long in hours this is done.
The air cooled Tecumseh I tried this on it was ~200F for longer that 45 minites to 1 hours under just an engine running load. Two dead engines.
Ha! Ha! Killed a third with intentional no ash separation/filtering testing.

Hi everyone, Just got the video put together that shows the Simple-Fire mounted on a genset. Here is the link:

I am working on another one that goes into detail on how the Simple-Fire unit is put together.
Something is happening that I need to figure out. The engine is getting harder to start and my thoughs are the charcoal gas isn’t rich enough. May also be a problem with the engine. Took me almost 10 minutes to get it started this AM. Used to take 4. Hopefully I will find the cause/causes.
Until later,
Gary in PA

I’m excited!!! Two weeks ago, I got my Gravely out and started to plow some new ground. The engine was fueled using the gasifier shown in the video and it just was not giving it enough power. I had to stop the tractor every few feet to let the engine rev up. I could not even go up the hill unless the machine was in low range. Oh, the air mixture valve was closed all the way too. If it was cracked open a little, the fuel was too lean. Kind of bummed out. A few days ago I had to mow some grass and did not have time to fiddle with the charcoal gas. Dino juice was used to get the mowing done. Figured I had two options. One was to just give up and go back to dino juice. The other option is to build a better charcoal gas generator. While loooking around behind my shop, I found a 10 gallon stainless steel milk can. This replaced the 5 gallon steel pail which will give me longer run time. I also put an oil drip to provide some hydrogen to the charcoal gas. The filter was also enlarged.
Wow, what a difference!!! I can now go up the hill in high range because the engine has much more power. It doesn’t take much used oil dripped into the air intake to make a difference.
If you use a simple-fire style of charcoal gasifier and you have access to used oil of any kind, I’d highly recommend installing the oil drip to boost the BTU value of the charcoal gas.
Here is a picture of the unit.

Gary, you are a genius. I’m still scavenging parts and pipe to hopefully attempt a gasifier, and my first will be a Gilmore Simple Fire! Your efforts into simplifying gasification has got to have had a profound effect on all considering gasification. It has got to be the first unit that anyone should build as an introduction to the ‘sport’. It seems dripping spent oil into the reaction zone is the turbo needed to boost power. I’ve been eyeing up an old moped 2T oil pump for the operation, should I get that far that is. Can’t get Brian Hughes idea out of my head of using an oil bath filter like the old British Leyland unit found in old Land Rovers. The unit could both filter the exiting gas and drip feed into the reaction zone, thus returning any trapped dust particles back into the furnace for a second try. In effect, a self cleaning filter (of sorts).

Wow; I finally got all of the past comments read. Didn’t realize this thread had been running for so long. I didn’t get to Argos this year. I was there last year and saw you but at the time I didn’t see any sense in making charcoal and wasting all the pyrolysis gases then but now I understand–SIMPLIFIED GASIFICATION! I have been working on a woodgas vehicle for years and I have had many disappointments and a few successes. I really haven’t made up my mind to drop the vehicles, but after watching your excellent videos, I feel it is a must that I understand all about charcoal and running small engines on it. I’m not a “picker” but I do fear that we could be in for some rough times. It appears that with about 4 or 5 hours of work I could get my generator running on charcoal — that beats several years like it has been for full gasification. So just a few questions come to mind. 1) Why do you prefer the double barrel method of making charcoal over putting a small barrel in a larger barrel with the openings along the bottom of both barrels and getting the pyrolysis off the wood to feed the fire. 2). You mention adding “pellets” into the charcoal during a run on charcoal gasifier. Is that correct/ok and why? 3). Finally {for now} It appears that even with the exhaust gas recirculated as the charcoal supply burns down the unit gets hotter. (to the point that you have to stop to keep from melting your hoses) In building a Simple gasifier, would it be better to build the unit taller rather than short and wider. My thinking right now is; the smaller diameter can, with equal amounts of charcoal, the gas would travel further vertically through the charcoal to get to the outlet, thus being cooler on exiting. (?) Or why does the gas get hotter as the charcoal burns down? Opps! 4.) Sorry. What is the limiting factor when it comes to adding exhaust gases? Is it that the more exhaust we add, the less oxygen we add cutting down on the combustion and thus cutting down on the manufactured gases. Keep up the GREAT work. (it was good, but don’t give up your day job to write music) PS. Man is there no end to the questions? 5). I realize the “oil drip” is a recent innovation, but how about a little more detail?

Hi Tom,
That was a lot of posts to read. The Simple-Fire thread was pretty active until the winter. Things kind of tapered off. I spent quite a bit of time in the shop running the Simple-Fire to power a larger gen set. Keeping track of run times, weight of charcoal used, trouble shooting problems, trying different nozzles, and so forth. At Argos, I was somewhat surprised by the amount of interest in the charcoal. A few guys saw it last year and felt the same way you did, but expressed more interest in it this year.
Making charcoal loses about half the energy value in the wood. With that said, it is a more refined fuel which has advantages. Waste is a relative term in some ways but will save that discussion for later. On to your “few” questions.

Why do you prefer the double barrel method of making charcoal over putting a small barrel in a larger barrel with the openings along the bottom of both barrels and getting the pyrolysis off the wood to feed the fire.
Answer. What you are describing is the indirect method of making charcoal. The wood you place around the inner barrel is set on fire to bring the wood in the retort up to heat. Once up to heat, the gasses given off from the wood in the retort will produce the heat to finish the charring. The wood you use to start the process is totally burned up and does not add to your final product. The direct method works well for me so I have never tried the other method. Let me put that on my list of things to do this summer. I should at least give it a try.
2). You mention adding “pellets” into the charcoal during a run on charcoal gasifier. Is that correct/ok and why?
Answer: That is correct, I add pellets, plastic, sawdust, deer poop, to my Kahle style charcoal gasifier. It has an air inlet that is centrally located on the top of the gas generator. Do not confuse this style with the Simple-Fire which has a nozzle entering at the bottom of the generator.
3). It appears that even with the exhaust gas recirculated as the charcoal supply burns down the unit gets hotter. That is correct. The depth of the charcoal above the hot oxidation zone is slowly being lowered as the charcoal is consumed. There comes a time when the layer of charcoal becomes insufficient to insulate and the heat comes through.

4). In building a Simple gasifier, would it be better to build the unit taller rather than short and wider. My thinking right now is; the smaller diameter can, with equal amounts of charcoal, the gas would travel further vertically through the charcoal to get to the outlet, thus being cooler on exiting. That is what I am thinking too. In fact my latest Simple-Fire is built out of a 40 gallon hot water tank. This gives me a much higher bed of fuel and therefore longer run times.

5). What is the limiting factor when it comes to adding exhaust gases? Is it that the more exhaust we add, the less oxygen we add cutting down on the combustion and thus cutting down on the manufactured gases. Answer: You can add too much engine exhaust gas. Too much will restrict the amount of oxygen available to react with the charcoal thereby lowering the temperature in the oxidation zone. If this temp drops below 1800F (have to pin this temp down better) the CO2 produced will not decompose into carbon monoxide. I am looking for a bright red heat.
6). I realize the “oil drip” is a recent innovation, but how about a little more detail?
Answer, Let me save this for tomorrow. I was using it last night while splitting wood and ended up turning it off. Still need to do some more experimenting.
Got to go, but will continue.
Gary in PA

Just wanted to say thank you Gary for answering my many questions. I moved my “tractor wood chunker” out of the shop to day and I ran across a steel 5 gal bucket.( old FEMA filter) It might get turned into a Gilmore Gasifier. Have to check and see if I can find any small barrels to make charcoal in. Everything on Cragis List is plastic barrels.

Gary G.: Let me begin by saying that I don’t mean to be presumptuous or to step on any toes.

I may have just thought of a way to further simplify the Simple-Fire (and keep the original drum/bucket intact!)

Instead of cutting a hole in the side of your drum and running your inlet pipe in horizontally, one cuts a second hole in the center of the lid and runs a longer inlet pipe in vertically. The inlet would be roughly 70-90% of the height of your drum (depending on size of optimal reaction area), plus some outside of the lid for mounting an exhaust return and/or oil drip, etc. This should place the reaction zone in roughly the same place as the standard set-up, IE in the middle, a little bit above the bottom of the drum.

The outlet would still be a short piece of pipe in the lid, but slightly off-set to one side to make room for the inlet. I don’t believe a small off-set would cause the reaction zone to burn unevenly. I’d probably put a small screen cage around the outlet nozzle to prevent any fines from getting sucked up into the outlet.

Hi Brian,
What you are describing is based on the Kalle style charcoal gasifier. I have been playing around with this design for about 8 years now. What you are showing in the diagram will definitely work. I use an auger to drop fuel down the air inlet pipe to augment the charcoal and add other fuels that contain hydrogen. (wood pellets, corn, sawdust, sunflower seeds, etc.) The system works well but it is not as simple to build (in my opinion) as the Simple Fire side nozzle. One big issue is getting the ceramic nozzle to stay on. I have used a stainless steel bolt to hold it in place, but the fire clay nozzle tends to crack where the bolt holds it on. Am trying out a newer setup where two stainless steel tabs hold the nozzle on. This was tried for the first time at the Argos meeting two weeks ago. Need more test time, but this is definately a system that will work and one that I had on my VW beetle before rust issues took it off the road.
Have you made any more test runs with your Simple-Fire?
Gary in PA (yes I do have steel toe shoes )

Gary G.: To be honest, I haven’t even tried to get a Simple-Fire going since my last post about it several months ago. The main reason is that my bipolar/depression got pretty bad for a while. I got discouraged by the RTV silicone I have that has yet to make a decent bucket gasket and the several failed side inlet flange attempts.

A second major issue is that I live in a town with a year-round ‘NO FIRES EXCEPT FOOD PREPERATION!’ burnban. I already have had 2 visits from the fire department from people whining when I have smoked some meats. I’m not sure I could get away with making any quantities of charcoal around here.

Brian Ham… I’ve had my best results with a vertical tuyere like you suggest, but I’ve been lucky enough to start with a supply of wide mouthed fire extinguishers with a 65mm internal thread on the top- getting a seal is much easier than with bucket top diameters. I put the tuyere centrally and suck the gas from round it.

Brian Hughes: I can’t say that I’ve seen one of those at the scrap yards. I can get a decent supply of 10 gallon vertical propane tanks for a few bucks each. I also know of a place that I can get 4" (101mm) mild steel pipe scraps for cheap. I think I should be able to make a servicable bolt-flange if I can find a small piece of good plate. My current sheet of steel is pretty rusted up now and I’m not sure how salvagable it is. I knew I should have put it in my “wood shed” instead of leaning against a tree outside all winter.

I decided to attempt a hybrid Simple Fire/Kalle gasifier in one of my 5 gallon steel buckets.

I cut out a circle out of the top of one of my closed-end barrels to reinforce the lid where the pipe and fittings will all be attached to. It wasn’t the prettiest of welding jobs, especially since I had several burn-throughs that needed to be patched with big globs of welding wire filler.

I used my biggest drill bit (a “#4 Unibit”, I think it goes up to 3/4 inch) to drill some holes for my pipes. The holes were still too small so I used some sheers to “flower” out the holes to the OD of the pipes (1" ID). The “flower petals” also give more grip on the pipe at the joint. I had some pretty nice looking welds on the pipe-to-lid joints but I wanted to over-build them which made them turn ugly.

Unfortunately, I was welding until after dark with a flashlight so I couldn’t take any “in progress” pictures.

Picture 1: Top of the lid showing reinforcement plate welded in. I chose to add some heatsink fins to the outlet pipe to cool some of the gas before it reaches the gas tube, which is a rubber radiator hose.

Picture 2: Bottom of the lid showing the internal lengths of the respective pipes. I still need something more heat-resistant to put on the end of the inlet pipe. I’ll probably salvage some stainless from one of my girlfriend’s old water bottles and wrap the tip with a few layers of that.

Picture 3: Close up of the heatsink on the exit pipe. I was pretty much just fucking around trying to get a workable method of sticking those banding fins to a pipe with minimal burn-through.

Picture 4: I warped the lid pretty decently while welding those things. I’ll have to take a rubber mallet and maybe my tiny bench-vise to straighten it out tomorrow.

Gary G: What kind of flex pipe/tubing are you using and how did you get it? All I can find are either >2"ID, plastic that’ll melt in a hot sun, aren’t air-tight, and/or only come in 6" lengths at 19$ a piece. Thoughts?